The most important thing of any compelling work of writing is the ability to make your story feel more... Realistic. Like, if this world actually existed these people could easily be believed to act throughout it. As such it is far more important to focus on the place where the story is than where it is supposed to be going.

Well, I believe being a good writer involves proper punctuation, character development, proper spelling, setting (time and place), and how the plot progresses, as well as if the writing fits the genre. Also, plot twists if they're executed properly.

I agree with Gamma. A writer who knows how to immerse their audience is a great writer!

A good writer has to have a good understanding of the words they choose to write with. I stop reading so many things I find because the sentences leave so much to be desired. Writers, when good, are masters of weaving a tapestry of words together to form the fabric of their story. Indulging in a thesaurus from time to time isn't enough. You need to really have a feel for what the words will emote, connote, and bring out within the context of your writing.

Know your audience that you want to reach and write in a way that you think will enthrall them. When I write I always think to myself, "Would I enjoy this if someone else wrote it?" since for my works I myself am part of that target audience. If I can't reread my own work and feel like it's capable of keeping me engaged it just isn't good enough. Writing for an audience that you don't fall into yourself makes things more difficult, but that just means you need to either train yourself to think in that mindset, or meet some people that fall into your target demographic.

(Message exceeded the post count I think.)

Write often, and read the works of others whenever you can. Imitate styles you enjoy and blend them with your own to develop a way of writing that's as unique as you can make it. I've worked on my "action-oriented" style that seeps into my role-playing since I started writing seriously back in the 8th grade. I read tons of fiction and had all sorts of story concepts that I would let float around my head until I decided to finally pick up a pencil and try to write myself.

Last thing I'll mention is getting honest constructive criticism as often as you can. Don't worry about how much you might be bugging those around you, or if you don't know if it's ready for other eyes yet. Once you finish a story the purpose is for it to be read by others and enjoyed, right? That's why the opinions of others are essential in increasing your skills as a writer. Be bold and ask for more details or in-depth looks at what you put out because only hearing "It's good" or "I like it" and other such positive and negative equivalents serves to stagnate you when a writer should be seeking to constantly improve.